Fix port_get_raw_ticks() for these ports:

o broadcom: return subticks
o cxd56: return subticks only when pointer is non-null
o litex: zero subticks, port is accurate only to ticks
o raspberrypi: correct subtick calculation

Author: eightycc

ports/broadcom/supervisor/port.c

@@ -143,7 +143,11 @@ uint64_t port_get_raw_ticks(uint8_t *subticks) {
     }
     COMPLETE_MEMORY_READS;
     uint64_t microseconds = hi << 32 | lo;
-    return 1024 * (microseconds / 1000000) + (microseconds % 1000000) / 977;
+    int64_t all_subticks = microseconds * 512 / 15625;
+    if (subticks != NULL) {
+        *subticks = all_subticks % 32;
+    }
+    return all_subticks / 32;
 }
 
 void TIMER_1_IRQHandler(void) {

ports/cxd56/supervisor/port.c

@@ -124,7 +124,9 @@ void board_timerhook(void) {
 
 uint64_t port_get_raw_ticks(uint8_t *subticks) {
     uint64_t count = cxd56_rtc_count();
-    *subticks = count % 32;
+    if (subticks != NULL) {
+        *subticks = count % 32;
+    }
 
     return count / 32;
 }

ports/litex/supervisor/port.c

@@ -114,6 +114,9 @@ uint64_t port_get_raw_ticks(uint8_t *subticks) {
     common_hal_mcu_disable_interrupts();
     uint64_t raw_tick_snapshot = raw_ticks;
     common_hal_mcu_enable_interrupts();
+    if (subticks != NULL) {
+        *subticks = 0;
+    }
     return raw_tick_snapshot;
 }
 

ports/raspberrypi/supervisor/port.c

@@ -491,11 +491,11 @@ static volatile bool ticks_enabled;
 static volatile bool _woken_up;
 
 uint64_t port_get_raw_ticks(uint8_t *subticks) {
-    uint64_t microseconds = time_us_64();
+    int64_t all_subticks = time_us_64() * 512 / 15625;
     if (subticks != NULL) {
-        *subticks = (uint8_t)(((microseconds % 1000000) % 977) / 31);
+        *subticks = all_subticks % 32;
     }
-    return 1024 * (microseconds / 1000000) + (microseconds % 1000000) / 977;
+    return all_subticks / 32;
 }
 
 static void _tick_callback(uint alarm_num) {